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Irrigants in endodontics

Simply discussed

A summary of 4 endodontic textbooks(Torabinejad &Walton, Pathways,

Weine and Ingle) and a review

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ByAhmed Mostafa Hussein

Assisstant lecturer Dental Biomaterials Department

Faculty of Dentistry, Mansoura University, Egypt

2014

ahmadmostafahussein3@yahoo.com

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Requirements and functions of irrigants

1. Dissolve organic and inorganic tissue.

2. Remove smear layer. (Pathway)

Disinfecting and cleaning areas inaccessible to endodontic instruments. (pathway)

3. Flush out and remove debris → prevent apical blockage by debris. (Ingle)

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4. Antimicrobial

5. Lubricant

6. Low surface tension

7. Don't weaken the tooth structure

8. Non-toxic and non-irritant

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Advantages of smear layer removal (Walton & Weine)

1. Allows penetration of irrigants into dentinal tubules.

2. Enhances penetration and adhesion of sealer to dentin.

3. Filling materials adapt better to the canal wall.

4. Reduces coronal and apical leakage.

N.B: The small particles of the smear layer are primarily inorganic. (Walton)

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Functions of lubricants (Pathway)

1. Facilitate the mechanical action of endodontic hand or rotary files

2. Increase cutting efficiency → better removal of debris

3. Reduce torque → the files and reamers are less likely to break (Weine)

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Types of irrigantsSaline, sodium hypochlorite (NaOCl),

chlorhexidine(CHX), Iodine potassium iodide (IKI),

hydrogen peroxide (H2O2), MTAD,

citric acid (CA),

EDTA (lubricant, decalcifying and chelating agent)

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* No single irrigating solution covers all of the functions required from an irrigant.

* The alternating use of different irrigants in the correct sequence contributes to a successful treatment outcome.

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1. Saline (Review)

* Lacks antibacterial activity when used alone.

* Doesn't dissolve tissue.

* Has the risk of contamination if used from containers that have been opened more than once.

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2. Sodium hypochlorite (NaOCl)* NaOCl is one of the most widely used irrigating solutions.

* Household bleach such as chlorox contains 5.25% NaOCl. (Ingle)

* Full strength (5.25%) NaOCl is highly irritating to

periapical tissues and reduces the flexural strength

& elastic modulus of dentin.

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* A common concentration of NaOCl is 2.5% which decreases toxicity and still maintains some tissue dissolving and antimicrobial activity.

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Advantages of NaOCl (Walton)

1. Dissolve organic tissue: NaOCl is the only root- canal irrigant that dissolves necrotic and vital organic tissue (unique property). (Review)

2. Antimicrobial action

3. Lubricant

4. Inexpensive and readily available

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Disadvantages of NaOCl

1. Irritant to periapical tissues, mucous membrane and skin. (Ingle)

2. Unpleasant odour.

3. Can damage clothes.

4. The use of NaOCl as the final rinse following EDTA or citric acid (CA) produces severe erosion of the canal-wall dentin and should be avoided.

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5. Causes haemolysis & ulceration, inhibits neutrophil migration and damages endothelial & fibroblast cells.

N.B: In vivo, the presence of organic matter (inflammatory exudate and tissue remnants) weakens NaOCl effect.

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3. Chlorhexidine (CHX)* Relative absence of toxicity. (Ingle)

* Broad spectrum antimicrobial substantive activity

(continued antimicrobial effect), because chlorhexidine (CHX) binds (is adsorped) and released gradually from the hydroxyapatite surfaces. (Review)

* 2% CHX has similar antimicrobial action as 5.25% NaOCl and is more effective against Enterococcus faecalis. (Walton)

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* Recent reports have indicated that several disinfecting agents such as CHX, Iodine potassium

iodide (IKI) and Ca(OH)2 are inhibited in the presence of dentin. (Pathway)

* The activity of CHX is greatly reduced in the presence of organic matter. (Review)

* CHX cannot be the main irrigant in standard endodontic cases, because CHX doesn't dissolve the smear layer or necrotic tissue. (disadvantage)

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Indications of CHX1) 2ry endodontic infections.

2) At the end of chemomechanical preparation, because CHX doesn't cause erosion of dentin like NaOCl does as the final rinse after EDTA.

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4. Iodine potassium iodide (IKI)

* Iodine is less cytotoxic & irritating to vital tissues than NaOCl & CHX, but obvious disadvantage of

iodine is a possible allergic reaction in some patients.

* 2 & 4% Iodine potassium iodide (IKI) has considerable antimicrobial activity, but no tissue- dissolving property. It can be used at the end of chemomechanical preparation like CHX.

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* Although Ca(OH)2 alone was unable to kill E. faecalis inside dentinal tubules, Ca(OH)2 mixed with either IKI or CHX effectively disinfected dentin (may be able to kill Ca(OH)2-resistant bacteria). (Pathway)

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5. Hydrogen peroxide (H2O2) (Weine)

* H2O2 destroys anaerobic microorganisms.

* The solvent action of H2O2 is less than that of NaOCl, so H2O2 is less damaging to periapical tissues.

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* Many clinicians use the solutions (H2O2 & NaOCl)

alternately during treatment. This method is strongly suggested for irrigating canals of teeth that have been left open for drainage, because the effervescence is effective in dislodging food particles & other debris that may have packed the

canal.

* H2O2 shouldn't be the last irrigant used in a canal,

because nascent oxygen may remain and cause pressure. Therefore NaOCl should be used to react with H2O2 and liberate the oxygen remaining.

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6. MTAD (Walton and review)

* Mixture of tetracycline isomer (doxycycline), an acid (citric acid) & detergent.

* Biocompatible.

* MTAD may be superior to NaOCl in antimicrobial action.

* MTAD is effective in killing E. faecalis found in failing treatments.

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* Although earlier studies showed promising antibacterial effects by MTAD, recent studies have indicated that NaOCl/EDTA combination is equally or more effective than NaOCl/MTAD. (Review)

* MTAD helps in removal of smear layer.

* MTAD doesn't dissolve organic tissue. (disadvantage)

* It doesn't alter physical properties of dentin.

* It could be used at the end of chemomechanical preparation after NaOCl. (Review)

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7. Citric acid (CA)

* EDTA & citric acid (CA) effectively dissolve inorganic material, including hydroxyapatite. (Review)

* Help in smear layer removal. (Walton)

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8. EDTA (ethylene diamine tetraacetic acid)

* Lubricant, chelator & decalcifying agents.

* EDTA is the most effective chelating agent in endodontic therapy.

* In general, files remove dentin faster than the chelators can soften the canal walls. (Walton)

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* 17% EDTA for 1 min remove inorganic components.

* EDTA is effective in smear layer removal only in coronal & middle thirds, but not in the apical third. N.B: NaOCl is necessary for removal of organic component.

* EDTA has little effect on periapical tissue.

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Disadvantage of EDTADeactivation of NaOCl by reducing the available chlorine. (Walton)

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Contraindications of EDTA (Weine page 225)

1) A ledged or blocked canal: If a sharp instrument is forced or rotated against a wall softened by the chelate, a new but false canal will be started.

2) Curved canals once the larger-sized instruments (size 30 or greater) are being used. These instruments are not as flexible as the smaller sizes and may produce root perforation.

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Indication of EDTA

The best use of chelating agents is to aid and simplify preparation for very sclerotic canals after the apex has already been reached with a fine instrument.

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*Chelating agents are placed in the orifice of a canal to be enlarged on the flutes of the enlarging

instrument or by plastic syringe .N.B: EDTA reacts with glass, so glass syringes of that material may not be used. (Weine pages 224 & 225)

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PrecautionEDTA will remain active within the canal for 5 days if not inactivated. If the apical constriction has been opened, the chelate may seep out & damage the periapical bone. For this reason, at the completion of the appointment, the canal must be irrigated with NaOCl to inactivate EDTA. (Weine page 226)

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Conventional irrigation by syringe

* Disposable 2.5 or 5 ml plastic syringes are useful for endodontic irrigation. (Weine)

N.B: Larger syringes are difficult to control for pressure, and accidents may happen. (Review)

* A commonly used needle is the 27-gauge needle with a notched tip, allowing for solution flowback, or the blunt-tip ProRinse. (Ingle)

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Notched tip

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Side port & rounded tip

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Selected video from youtube:

www.youtube.com/watch?v=3FVXN1sCKf8

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* All syringes for endodontic irrigation must have a Luer-Lok design. (Review)

* The irrigating needle must be placed loosely in the canal. To control the depth of insertion, the needle is bent slightly at the appropriate length or a rubber stopper is placed on the needle. (Walton)

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Luer-Lok design

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* Irrigants must be gently placed within the canals. It is the action of intracanal instruments that distributes the irrigant into the canal. (Weine)

* The needle is moved up and down constantly to produce agitation & prevent binding or wedging of the needle. (Walton)

N.B: Severe complications have been reported from forcing irrigating solutions beyond the apex by wedging the needle in the canal and not allowing an adequate backflow. (Ingle)

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* The irrigant doesn't move apically more than 1 mm beyond the irrigation tip. (Walton)

* The closer the needle tip to the apex, the greater the potential for damage to the periradicular tissues.

* The volume of irrigant is more important than the concentration or type of irrigant. (Ingle page 502)

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* The apical 5 mm are not flushed until they have been enlarged to size 30 and more often size 40 file. (Ingle)

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* Separate syringes should be used for each irrigant to avoid chemical reactions between them. (Review)

* N.B: Ultrasonics proved superior effect to syringe irrigation alone when the canal narrowed to 0.3 mm (size 30 instrument) or less. (Ingle)

* N.B: The US Army reported the importance of recapitulation–re-instrumentation with a smaller instrument following each irrigation. (Ingle page 503)

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Questions

What are the irrigants that can be used for final irrigation and why?

* CHX, IKI and MTAD can be used at the end of chemomechanical preparation, because they doesn't cause erosion of dentin.N.B: Some patients have allergy to iodine.N.B: CHX has continued antimicrobial activity, why?

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* What are the irrigants that cannot be used for final irrigation and why?

1) EDTA: why?

2) NaOCl: why?

3) H2O2: why?

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Main references1. Torabinejad M, Walton RE. Endodontics principles and practice. 4th ed. Saunders; 2009. p. 391-404.

2. Cohen S, Hargreaves KM. Pathways of the pulp. 9th ed. St. Louis: Mosby; 2006. p. 318-323.

3. Ingle JI,Bakland LK. Endodontics. 5th ed. BC Decker; 2002. p. 498-505.

4. Weine FS. Endodontic therapy. 6th ed. St. Louis: Mosby; 2004. p. 221-226

5 .Haapasalo M, Shen Y, Qian W, Gao Y. Irrigation in endodontics. Dent Clin N Am. 2010; 54: 291-312. (Review)